linux-kernel - Re: [PATCH V8 06/10] acpi: apei: panic OS with fatal error status block

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Message-ID: <58A445D5.7030501@arm.com>
Date:   Wed, 15 Feb 2017 12:13:09 +0000
From:   James Morse <james.morse@....com>
To:     "Baicar, Tyler" <tbaicar@...eaurora.org>, zjzhang@...eaurora.org
CC:     christoffer.dall@...aro.org, marc.zyngier@....com,
        pbonzini@...hat.com, rkrcmar@...hat.com, linux@...linux.org.uk,
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Subject: Re: [PATCH V8 06/10] acpi: apei: panic OS with fatal error status
 block

Hi Tyler,

On 13/02/17 22:45, Baicar, Tyler wrote:
> On 2/9/2017 3:48 AM, James Morse wrote:
>> On 01/02/17 17:16, Tyler Baicar wrote:
>>> From: "Jonathan (Zhixiong) Zhang" <zjzhang@...eaurora.org>
>>>
>>> Even if an error status block's severity is fatal, the kernel does not
>>> honor the severity level and panic.
>>>
>>> With the firmware first model, the platform could inform the OS about a
>>> fatal hardware error through the non-NMI GHES notification type. The OS
>>> should panic when a hardware error record is received with this
>>> severity.
>>>
>>> Call panic() after CPER data in error status block is printed if
>>> severity is fatal, before each error section is handled.

>>> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
>>> index 8756172..86c1f15 100644
>>> --- a/drivers/acpi/apei/ghes.c
>>> +++ b/drivers/acpi/apei/ghes.c
>>> @@ -687,6 +689,13 @@ static int ghes_ack_error(struct acpi_hest_generic_v2
>>> *generic_v2)
>>>       return rc;
>>>   }
>>>   +static void __ghes_call_panic(void)
>>> +{
>>> +    if (panic_timeout == 0)
>>> +        panic_timeout = ghes_panic_timeout;
>>> +    panic("Fatal hardware error!");
>>> +}
>>> +

>> __ghes_panic() also has:
>>>     __ghes_print_estatus(KERN_EMERG, ghes->generic, ghes->estatus);
>> Which prints this estatus regardless of rate limiting and cache-ing.

[...]

>>>               ghes_estatus_cache_add(ghes->generic, ghes->estatus);
>>>       }
>>> +    if (ghes_severity(ghes->estatus->error_severity) >= GHES_SEV_PANIC) {
>>> +        __ghes_call_panic();
>>> +    }

>> I think this ghes_severity() then panic() should go above the:
>>>     if (!ghes_estatus_cached(ghes->estatus)) {
>> and we should call __ghes_print_estatus() here too, to make sure the message
>> definitely got out!


> Okay, that makes sense. If we move this up, is there a problem with calling
> __ghes_panic() instead of making the __ghes_print_estatus() and
> __ghes_call_panic() calls here? It looks like that will just add a call to
> oops_begin() and ghes_print_queued_estatus() as well, but this is what
> ghes_notify_nmi() does if the severity is panic.


I don't think the queued stuff is relevant, isn't that just for x86-NMI messages
that it doesn't print out directly?

A quick grep shows arm64 doesn't have oops_begin(), you may have to add some
equivalent mechanism. Lets try and avoid that rabbit hole!

Given __ghes_panic() calls __ghes_print_estatus() too, you could try moving that
into your new __ghes_call_panic().... or whatever results in the least lines
changed!


Thanks,

James